Widespread Sensitivity of Grassland Water Use Efficiency to Deep Soil Moisture on the Tibetan Plateau

作者：Yang Liu, Cheng Chen, Qiuwen Chen, Jianyun Zhang, Zhen Cui, Zhenzhong Zeng · 发表于：Water Resources Research · 年份：2025 · DOI：10.1029/2024wr038645 · 被引用次数：12 · 研究领域：Climate change and permafrost、Cryospheric studies and observations、Soil Moisture and Remote Sensing

Abstract Water use efficiency (WUE, the ratio of gross primary productivity to evapotranspiration (ET)) is a robust indicator of ecosystem response to climate change, with soil moisture serving as a crucial determinant. Soil moisture varies across soil layers due to ET and soil structure, thereby differentially impacting vegetation. However, the influence of soil moisture at various soil layers on grassland WUE remains poorly understood. Using random forest and Shapley additive explanations, we examined grassland WUE sensitivity to soil moisture at different soil layers across alpine meadow and steppe ecosystems on the Tibetan Plateau. We found that grassland WUE was more sensitive to deep soil moisture (deepSM) than surface (surSM) and middle (midSM) over 2001–2020. Structural equation modeling indicated deepSM was less influenced by temperature, vapor pressure deficit (vpd) and wind speed (ws), thus providing more stable water to vegetation and exerting greater influence on WUE under the same moisture change. Additionally, alpine steppes exhibited lower sensitive to soil moisture than alpine meadows due to greater ecological adaptations and deeper root systems. Over time, WUE sensitivity to deepSM remained stable, whereas sensitivity to surSM and midSM significantly decreased in both grassland types on the Tibetan Plateau. This decrease in WUE sensitivity to surSM and midSM was associated with increased precipitation, decreased ws, and increased vpd. These findings highligh...